Light source for photographic printer

ABSTRACT

An improved light source for a photographic printer uses a plurality of print lamps. A heatsink and blower dissipate heat generated by the print lamps. The light diffuser which diffuses light from the lamp includes a white porcelain diffuse reflector.

REFERENCE TO CO-PENDING APPLICATIONS

Reference is made to co-pending applications entitled "Paper Feed Systemfor Photographic Printer," Ser. No. 776,876; "Paper Feed Cut off forPhotographic Printer", Ser. No. 776,930; "Test System for PhotographicPrinter," Ser. No. 776,873; and "Photographic Printer," Ser. No. 776,877in which subject matter disclosed but not claimed in this application isdisclosed and claimed. These co-pending applications are assigned to thesame assignee as the present application.

BACKGROUND OF THE INVENTION

The present invention is concerned with photographic printing systems.In particular, the present invention relates to an improved light sourcefor use in photographic printing systems.

Photographic printers produce color or black and white prints fromnegatives. High intensity light is passed through a negative and imagedon photographic print paper. A photographic emulsion layer on the printpaper is exposed and subsequently processed to produce a print of thescene contained in the negative.

Photographic processing centers typically process film from manycustomers. The printers used in these processing centers must be capableof producing color and black and white prints from a range of negativesizes which include, for example, 110, 120, 126, 35mm, 70mm and 21/4 ×31/4 inches negative sizes. The desired prints may have ten or moredifferent sizes and may be either with or without a border. In addition,some of the orders call for multiple prints from a single negative.

In order to increase efficiency and minimize the time required tofulfill customer orders, high speed printers in which many exposures aremade on a single roll of print paper are desirable. After the manyexposures are made, the portion of the roll which has been exposed isremoved from the printer, is photoprocessed to produce prints, and iscut to individual prints. The prints are then sorted by customer orderand ultimately packaged and sent to the customer.

The light source in a photographic printing system plays an importantrole in determining the overall efficiency of the system. Higherintensity light from the light source allows shorter exposure times andfaster operation of the printer.

The typical prior art photographic printer has used a single pointsource of light for its light source. The light from the point sourcepasses through dichroic filters and is then diffused by a diffuserchamber. Although this type of light source has been generallysatisfactory, a light source capable of higher intensity is desirable.

SUMMARY OF THE INVENTION

The improved light source of the present invention achieves higher lightintensity without a corresponding increase in input power consumption.The light source includes a plurality of print lamps rather than asingle point source. Heat from the plurality of print lamps isdissipated by heatsink means positioned around the lamps and blowermeans. Diffuser means diffuses the light from the plurality of printlamps to provide essentially uniform light distribution at the negative.

In a preferred embodiment, the diffuser means includes a white porcelaindiffuse reflector. It was discovered that materials used as diffusereflectors in prior art printers could not withstand the intense lightand heat produced by the plurality of print lamps.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the photographic printer of the present invention.

FIG. 2 schematically shows the optical system of the printer.

FIG. 3 shows the controls located on the operator panel.

FIG. 4 shows the controls located on the control panel.

FIGS. 5a-5c show the lamphouse.

FIGS. 6a and 6b show the color mixing chamber.

FIGS. 7a and 7b show the neghold and preview station.

FIGS. 8a and 8b show a typical negative mask or carrier.

FIG. 9 is a rear view of the cabinet, showing the lensdeck and paperdeckpositioning systems.

FIGS. 10a and 10b show the lensdeck assembly.

FIGS. 11a-11c are rear, left side, and partial right side views of thepaperdeck.

FIGS. 12a and 12b show the core guide assembly.

FIG. 13 shows a typical paper mask.

FIGS. 14a and 14b show a universal paper mask.

FIG. 15 schematically shows the control panel.

FIG. 16 shows a schematic diagram of the senior ring.

FIG. 17 is a schematic diagram of one of the three exposure controlcircuits.

FIG. 18 is a schematic diagram of a typical solenoid driver circuit.

FIG. 19 is a schematic diagram of the aperture pulse circuit associatedwith the paper feed system.

FIGS. 20a and 20b schematically show the paper feed circuitry.

FIGS. 21a and 21b schematically show the cycle control circuitry of theprinter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS System Overview

The photographic printer of the present invention produces color orblack and white prints from a range of negative sizes, including variousformats of 110, 120, 126, 35mm, 70mm and 21/4 × 23/4 inch negatives. Theprints are made on a roll of photographic print paper up to 250 feetlong in 31/2, 5, 8, and 9.4 inch widths.

FIG. 1 shows the printer of the present invention. The printer includesa cabinet 10, which houses most of the printer mechanism, a console 12on top of cabinet 10, and a lamphouse 14 and a color mixing chamber 16mounted on console 12.

Console 12 has two recessed panels, operator panel 18 and control panel20, which contain various switches and dials. These switches and dialsprovide the operator with options such as manual or automatic exposurecontrol, manual or automatic paper feed, multiple or single prints pernegative, and printer-governed or operator-governed exposure times.

Lamphouse 14 contains two print lamps which provide high intensitylight. Three pairs of dichroic filters in lamphouse 14 modify the colorbands of the light to provide near synchronized exposure times. Thelight is mixed in mixing chamber 16 and directed downward to provideessentially uniform light distribution at the negative, which is held ina negative mask or carrier (not shown) in neghold 21 beneath mixingchamber 16.

The light passes through the negative and is focused by a lens onto theprint paper. A paper mask defines the size and format of the print onthe print paper. A photocell sensor ring and associated electronic logicgauge the light passed through the negative and determine when theexposure of each paper emulsion layer is to be terminated. Filterpaddles below the lens are driven into the light path to terminate theexposure of each color.

Lensdeck adjustment handwheel 22 on the left side of cabinet 10 allowsadjustment up and down of the lens and lensdeck by means of lensdeckcounter 24 on the left side of console 12. Lensdeck counter 24 is afour-digit counter driven by the lensdeck pulley. The count on lensdeckcounter 24 is used for reference in setting the position of thelensdeck.

On the right side of cabinet 10 is a paperdeck adjustment handwheel (notshown) which adjusts the paperdeck up and down. Paperdeck counter 26, afour-digit counter on the right side of console 12, is for reference insetting the paperdeck position. By positioning the lensdeck andpaperdeck, proper focus and magnification for a variety of negative andprint sizes is achieved.

A preview area 28 is also provided on console 12. The negative andnegative carrier are placed over preview area 28, where the negative maybe viewed. A preview lamp beneath preview area 28 provides light toallow the operator to frame the negative properly in the negative mask.Printing is commenced by moving the negative and negative carrier frompreview area 28 to the print position under mixing chamber 16.

An important advantage of the printer of the present invention is thatall operations, except paper loading/unloading and changing paper masks,may be accomplished under normal room light rather than darkroomconditions. Lensdeck, paperdeck, color density, dichroic filter, paperfeed, and print counter controls are readily accessible without openingcabinet 10. Digital indicators for each control (such as lensdeckcounter 24 and paperdeck counter 26) provide ease of repeatability whensetting up the printer.

Optical System

FIG. 2 is a schematic diagram of the optical system of the printer. Theoptical system includes a pair of printlamps 32, three pairs of dichroicfilters 34, mixing chamber 6, negative masks 36, photocell sensor ring38, lens 40, shutter paddle 42 and filter paddles 44.

Printlamps 32 operate at low intensity prior to commencement of a printcycle. When the print cycle begins, they increase to high intensityuntil the exposure is completed.

The three pairs of dichroic filters 34 in the lamphouse are cyan(farthest from printlamps 32), magenta (center), and yellow (nearestprintlamps 32). Each pair of filters can be moved into or out of thelight path by controls on the lamphouse to modify the colors of thelight. For black and white printing, the filters are either moved out ofthe light path entirely or only the magenta filters are placed in thelight path. The magenta filters improve contrast of black and whiteprints.

Light from the lamphouse enters mixing chamber 16. "Hot spots" in thelight beam are diffused by a circular diffuser in chamber 16. Inaddition, a diffusion plate at the bottom of chamber 16 distributes thelight evenly across negative 46.

Negative mask 36 is one of a set of masks of various sizes adapted tohold negative 46. The size and format of negative 46 dictate theparticular negative mask used.

Photocell sensor ring 38 is positioned below negative 46 to receivescattered light from negative 46. Most of the light passes unimpededthrough ring 38 to lens 40. During normal, automatic operation,photocell sensor ring 38 operates to alter the exposure time called forby the color controls, according to the actual colors in negative 46.

Lens 40, shutter paddle 42, filter paddles 44, a bellows (not shown),and other associated hardware form the lensdeck of the printer. Thelensdeck position may be moved up and down to achieve proper focus byusing the lensdeck adjustment handwheel 22 (shown in FIG. 1).

Lens 40 is one of several interchangeable lenses which may be used tofocus the image from the negative onto print paper 48. The particularlens selected is determined by negative size and the print size.

Shuttle paddle 42 is normally in position in the light path below lens40. At the beginning of an exposure, shutter paddle 42 is moved out ofthe light path. The exposure is discontinued by shutter paddle 42 whenthe longest running color has finished its exposure time.

Filter paddles 44, which normally rest out of the light path, limit theexposure in specific color channels. When the exposure in the red,green, or blue channel is completed, the cyan, magenta, or yellow filterpaddle is driven into the light path. During black and white printing,filter paddles 44 remain out of the light path and do not function.

The paperdeck includes a paper drive mechanism (not shown) for advancingand taking up print paper 48 as successive prints are made. Paper mask50 defines the size and format of the prints. The paperdeck may beadjusted up and down to achieve proper focus and magnification of theimage from negative 46.

Printer Controls

The printer of FIG. 1 includes a variety of controls with which theoperator can modify and control the operation of the printer. Operatorpanel 18, control panel 20, and lamphouse 14 each have external controlsfor operator use.

FIG. 3 shows operator panel 18. The controls shown in FIG. 3 are POWERswitch 52, EXPOSE switch 54, CLEAR switch 56, PAPER switch 58,PRINT-FOCUS switch 60, COLOR-B/W switch 62, RUN-TEST switch 64, previewlamp control 66, color controls 68a, 68b and 68c, COARSE density control70, and FINE density control 72.

POWER switch 52 turns the printer power supply and lamphouse fan on andoff. As shown in FIG. 3, POWER switch 52 is a rocker switch which is inthe power-on position when rocked to the right and is in the power-offposition when rocked to the left. When POWER switch 52 and a LAMP switchon lamphouse 14 are both on, the pilot lamp is lit.

EXPOSE switch 54 is a momentary switch which, when depressed by theoperator, initiates one or more print cycles. The number of print cyclesis determined by a multiple print counter located on control panel 20.The operation of EXPOSE switch 54 is limited by a Microswitch whichsenses whether a negative mask is in place. If a negative mask is not inposition in the printer, depressing EXPOSE switch 54 causes only theprint lamps to increase to high intensity. The remainder of the printcycle will not occur unless a negative mask is inserted.

CLEAR switch 56 is a momentary switch which clears the electronic logicif an exposure or paper feed cycle is begun but not completed. After thelogic is cleared, a new print cycle may be attempted.

PAPER switch 58 is a momentary switch which initiates a paper feedcycle. The distance the paper travels is determined by either indica onpapermask 50 (automatic operation) or digital paper feed count switcheson control panel 20 (manual operation). While the paper is advancing andthe LAMP switch (on lamphouse 14) is on, an indicator lamp 74 to theright of PAPER switch 58 is on.

PRINT/FOCUS switch 60 is a rocker switch which, when in the PRINTposition (rocked left) allows normal operation of the printer.PRINT/FOCUS switch 60 must be in the PRINT position during printing.

The FOCUS position (rocked right) of PRINT/FOCUS switch 60 is used onlywhile focusing the printer. In FOCUS, print lamps 32 are increased tohigh intensity and shutter paddle 42 swings out of the light path. Anindicator lamp 76 to the right of PRINT/FOCUS switch 60 lights whenPRINT/FOCUS switch 60 is in the FOCUS position.

COLOR-B/W switch 62 selects a color or black and white printing mode forthe printer. In the black and white mode, only the blue circuitry,yellow color controls, and density controls function. Only the densitycontrols are used for density modification. In the color mode, allcircuits, color controls and density controls function.

RUN/TEST switch 64 enables or disables the automatic paper feedcircuitry and shutter paddle 42. In TEST, the function of the color anddensity controls may be checked. The function of shutter paddle 42 isdisabled. No paper is exposed while RUN/TEST switch 64 is in the TESTposition. RUN/TEST switch 64 must be in the RUN position duringprinting.

Preview lamp control 66 is a control knob which increases the intensityof the preview lamp with a clockwise turn. A counterclockwise turndecreases preview lamp intensity.

Control controls 68a, 68b, and 68c regulate the exposure time for thered, green and blue emulsion layers of the photographic print paper. Aclockwise turn of a color control knob increases color density.

Indicator lamps 78a, 78b and 78c, which are located to the lower rightof color controls 68a, 68b and 68c, respectively, show the duration ofthe exposure in that color channel. When the exposure begins, all threeindicator lamps light. Each goes out as the exposure in its colorchannel is completed. For black and white printing, indicator lamp 78cshows the exposure duration.

COARSE and FINE density controls 70 and 72 regulate the exposure time ofthe printer. In the embodiment shown in FIG. 3, each increment of COARSEdensity control 70 yields an exposure time twice as long and a densityincrease of 0.7 points from the setting below it. Each increment on theFINE density control 72 increases exposure time about 5 percent and thedensity about 0.04 points above the setting below it.

FIG. 4 shows the controls located on control panel 20. The controlsinclude MULTIPLE PRINT counter 80, PAPER FEED COUNT switches 82, PAPERAUTO/MAN switch 84, EXPOSURE AUTO/MAN switch 86, and SENSORS ON/OFFswitch 88.

MULTIPLE PRINT counter 80 can be set for any number of prints up to99,999. The printer will make that number of prints (of the samenegative) automatically after an exposure is initiated.

To set MULTIPLE PRINT counter 80, button 90 to the left of counter 80 isdepressed and held. Each of the buttons 92a - 92c below each digit ofcounter 80 is depressed and released as many times as necessary untilthe required number is registered. Button 90 is then released.

When a multiple print cycle is initiated, the printer will make thenumber of prints registered on counter 80. With each print, the numberon counter 80 is decremented by one. When the number on counter 80reaches "00000," the multiple print cycle is terminated. Depressingbutton 90 resets counter 80 to the number previously set.

If the multiple print cycle stops for some reason prior to reaching"00000," counter 80 freezes in position. When printing is resumed, theprinter will cycle the number indicated on counter 80.

PAPER FEED COUNT switches 82 control the length of paper feed when PAPERAUTO/MAN switch 84 is in the "MAN" position. PAPER FEED COUNT switches82 are three 10-position thumbwheel switches (settings 0 through 9). Ina preferred embodiment, increasing switches 82 one position produces thefollowing increase in paper feed travel: right switch 0.5 mm, centerswitch 5 mm, and left switch 50 mm.

PAPER AUTO/MAN switch 84 controls the mode of paper feed. In the "MAN"position, paper feed length is controlled by PAPER FEED COUNT switches82. The paper feed in AUTO is controlled by indicia associated with thepaper mask which is in use.

EXPOSURE AUTO/MAN switch 86 enables or disables the automatic printingcycle. When in AUTO, the print cycle begins when a negative mask isinserted in position in the neghold base. In MAN, EXPOSE switch 54 onoperator panel 18 must be depressed to start the print cycle.

SENSORS ON/OFF switch 88 controls the photocells of photocell sensorring 38 of the lensdeck. With the switch ON, the photocells determinethe exposure times in each color channel. With the switch OFF, thephotocells are disabled, and the exposure times are fixed and can becontrolled by color controls 68a, 68b and 68c and density controls 70and 72.

The remaining external controls are the paperdeck and lensdeckadjustment handwheels located on cabinet 10, and a LAMP ON/OFF switchand DICHROIC FILTER controls located on lamphouse 14.

The LAMP ON/OFF switch turns on the print lamps, the preview lamp, a"power on" indicator lamp and a digital timing clock (when present). Theprint lamps 32 operate at low intensity until a print, focus, or testcycle is begun. When the LAMP ON/OFF switch is OFF, all lights on theprinter are off, enabling loading/unloading of the print paper (when theroom is darkened) without turning the printer off.

The DICHROIC FILTER controls are located on the side of lamphouse 12 tocontrol the position of dichroic filters 34 in the light path. Afour-digit counter is associated with the control knob for each filterto assist in setting the filters on a consistent basis.

Mechanical System

FIG. 5-14 show various portions of the mechanical system of the printer.The mechanical system will be described in a "top-down" order, beginningwith the lamphouse and ending with the paperdeck and paper masks.

(1) Lamphouse

FIGS. 5a-5c show front, partial cutaway top and side views,respectively, of lamphouse 14. Print lamps 32a and 32b produce the highintensity light required for photographic printing. The light passesthrough the dichroic fiter assembly 34, which modifies the color of thelight, and out of the lamphouse through window 90.

Lamps 32a and 32b generate a substantial amount of heat which must beremoved from the lamphouse. Heatsink 92 is a blackened, baffled assemblywhich is mounted around the lamps. In addition, a cooling fan is mountedwithin the heatsink 92 behind lamps 32a and 32b. Fan cover 94 in therear of lamphouse 14 is baffled to assist in the cooling.

On the front surface of lamphouse 14 is the LAMP ON/OFF switch 96. Asdescribed previously, LAMP ON/OFF switch 96 turns on the print lamps,the preview lamp, the power on pilot lamp, and a timer clock (whenpresent).

On the right side of lamphouse 14 are controls 98 and 98c, which controlthe position of the cyan, magneta and yellow dichroic filters. Controls98a-98c each include a setting knob and a four-digit counter.

(2) Color Mixing Chamber

FIGS. 6a and 6b show top and cross-sectional side views, respectively,of color mixing chamber 16. The purposes of color mixing chamber 16 are(1) to change the direction of the light from horizontal (when leavinglamphouse 14) to vertical downward into cabinet 10, and (2) to mix anddiffuse the light to remove "hot spots" and provide a uniform lightdistribution at the negative.

Light from lamphouse 14 enters chamber 16 through opening 100, whichmatches window 90. The light is reflected downward by diffuse reflector102. Diffuser assembly 104 further diffuses the light before it passesout the bottom of chamber 16.

Diffuse reflector 102 is preferably a white porcelain member. It hasbeen discovered that white porcelain provides the desired diffusereflection and is capable of withstanding the very intense radiationfrom lamps 32a and 32b. Other diffuse reflector materials, such asstyrofoam, degrade when exposed to the very intense radiation.

Diffusion within chamber 16 is further aided by styrofoam members 106,108, 110, 112 and 114 on the walls of the chamber 16. The styrofoammembers act as diffuse reflector for light which strikes the walls ofthe chamber 16.

Diffuser assembly 104 is a circular ground glass diffuser which issupported by wires 116. Light is distributed evenly across the negativeby diffuser assembly 104.

(3) Neghold, Preview Station and Negative Mask

FIGS. 7a and 7b show top and left side views of the neghold 21 andpreview station 28. The negative is held in a negative mask (not shown),which is moved into place in neghold 21 by sliding the mask under rollerassemblies 118a and 118b. Stops 120a and 120b define the rear limit forthe negative mask.

Microswitch 122 near the rear of the neghold 21 is depressed when anegative mask is in place in neghold 21. The operation of the EXPOSEswitch 54 on operator panel 18 (FIG. 3) is inhibited when microswitch122 is not depressed. When the negative mask is not in position,depressing the EXPOSE switch causes only the print lamps 32a and 32b toincrease to high intensity. The remainder of the print cycle does notoccur until the negative mask is inserted in neghold 21 and microswitch122 is depressed.

The preview station 28 includes a white translucent plastic plate 124which is mounted over a preview lamp (not shown). Prior to sliding thenegative mask into the neghold, the negative and negative mask arepositioned over plate 124 where the negtative can be viewed by theoperator.

FIGS. 8a and 8b show top and side view of a typical negative mask 36 foruse with the printer. Mask 36 is a hinged, two-piece assembly which canbe slid under roller assemblies 118a and 118b of neghold 21.

A negative is inserted between top 126 and bottom 128 plates of mask 36.Top and bottom plates 126 and 128 have an opening 130 through whichlight can pass. The size of opening 130 is determined by the size of theparticular negative to be held. The negative is positioned under opening130 is top plate 126.

Mask 36 is inserted into position in neghold 21 by pushing members 132and 134 so that mask 36 slides under roller assemblies 118a and 118b.Notch 136 in mask 36, which is aligned with microswitch 122 of neghold21, ensure that microswitch 122 is not depressed until mask 36 has beenpushed all the way to the rear of neghold 21.

(4) Lensdeck and Paperdeck Positioning System

FIG. 9 shows a rear view of cabinet 10. The rear doors have been removedfor clarity.

Lensdeck 136 and paperdeck 138 each may be moved up and down along sliderails 140 and 142. Movement of lensdeck 136 and paperdeck 138 allowsadjustment of focus of the printer for the wide variety of negativesize-print size combinations which may be desired.

Lensdeck 136 includes the lens, shutter paddle and filter paddleassemblies which are attached to lensdeck carriage 143 and which will bedescribed in detail in a later section. Lensdeck 136 also includes arectangular shaped bellows 144. As lensdeck 136 is moved downward,bellows 144 is extended; as lensdeck 136 is moved upward, bellows 144contracts.

Movement of lensdeck 136 is produced by turning lensdeck adjustmenthandwheel 22. The turning of handwheel 22 causes rotation of shaft 146,which drives helical lead screw 148 through a helical gear. Lead screw148 passes through threaded member 150, which is fixed to lensdeck 136.Rotation of lead screw 148, therefore, causes lensdeck 136 to moveeither up or down on rails 140 and 142, depending on the direction ofrotation.

Rotation of shaft 146 also drives a pulley 152, which in turn driveslensdeck counter 24. The count on lensdeck counter 24 is used forreference in setting the position of lensdeck 136.

Adjustment of the position of paperdeck 138 is generally similar to theadjustment of the lensdeck position. A paperdeck adjustment handwheel152 adjusts the position of paperdeck 138. Rotation of handwheel 152and, therefore, shaft 154 drives helical lead screw 157 through a secondhelical gear. Lead screw 156 passes through threaded member 158, whichis attached to paperdeck 138.

Movement of paperdeck 138 is assisted by coil-type negator spring 160.The weight of paperdeck 138 is counteracted by negator spring 160, sothat the entire weight of paperdeck 138 is not resisting movement byhandwheel 152.

Shaft 154 also drives pulley 162, which in turn drives paperdeck counter26. The count on paperdeck counter 26 may be used in setting theposition of paperdeck 138.

(5) Lensdeck

FIGS. 10a and 10b show top and side views of the lensdeck assembly whichis attached to lensdeck carriage 143 (FIG. 9). The lensdeck assemblyincludes photocell sensor ring 38, lens and lens mount 40, shutterpaddle 42, and filter paddles 44.

Photocell sensor ring 38, which is mounted over lensdeck plate 164 byspacer 166 includes 10 photocells 168a-j, positioned in a ring aroundopening 170. Most of the light from the negative passes through opening170, but a portion of the light is sensed by photocells 168a-j. In onepreferred embodiment, photocells 168a-j are CdS photocells with filtersover each cell to limit the spectral response to red, blue or green. Thephoto signals from the photocells are used to control exposure time forthe various colors.

Lens and lensmount 40 is held in position by permanent magnet 172. Themagnetic field of permanent magnet 172 is strong enough to allow lensand lensmount 40 to hang bellow magnet 168. The use of magnet 172simplifies mounting and changing of lenses in the printer.

Shutter paddle 42 is driven into and out of the light path by solenoid174. The three filter paddles 44 are driven into and out of the lightpath by solenoids 176, 178 and 180.

(6) Paperdeck and Paper Mask

The printer of the present invention requires a paper drive mechanismwhich advances the paper by the proper amount between print cycles sothat successive prints do not overlap and yet are not so spaced apartthat print paper is wasted. From both a cost and reliability standpoint,the paper fed mechanism should be as simple as possible.

FIGS. 11a, 11b and 11c show rear, left side and partial right sideviews, respectively, of the paperdeck of the printer of the presentinvention. The paper drive mechanism of the paperdeck includes papersupply roller 182, supply metering roller 184, pressure roller 186,take-up metering roller 188, take-up roller 190, brake 192 and motor194.

The print paper is fed from a paper roll (not shown) which is press fitonto paper supply roller 182, between supply metering roller 184 andpressure roller 186, under light shield 196, across the top surface 198of the paperdeck, under paper mask 50, under light shield 200, overtake-up metering roller 188, and onto take-up roller 190. A significantadvantage of this system is that the paper drive is achieved by a singlemotor 194, which drives take-up roller 190. Advance of the paper ishalted by signals to both motor 194 and brake 192, which halts rotationof paper supply roller 182.

The paper drive mechanism shown in FIGS. 11a-11c accommodates printpaper of several different widths. Paper supply roller 182 and take-uproller 190 have several similarly spaced grooves. For example, papersupply roller 182 has grooves 202 and 204, as well as shoulder 206, andtake-up roller 190 has similarly spaced grooves and shoulder. A guidering 208 is positioned on paper supply roller in the appropriate groovefor the particular width of paper roll to be used. A similar guide ringis positioned in the comparable groove on take-up roller 190. FIGS. 12aand 12b show a typical guide ring.

Supply metering roller 184 and take-up metering roller 188 also have aplurality of spaced grooves. Slip rings 210 and 212 are positioned inthe appropriate grooves in roller 184 for a particular paper width, andtwo similar slip rings are placed on roller 188.

The loading of print paper is as follows. First, the guide rings arepositioned on supply roller 182 and take-up roller 190. Second, the sliprings are positioned on rollers 184 and 188. Third, an empty paper coreis pushed onto take-up roller 190 until stopped by the guide ring.Fourth, a print paper roll with the emulsion side out, is pushed ontosupply roller 182 until stopped by guide ring 208. Fifth, the paper isthreaded between supply metering roller 184 and pressure roller 186.Slip rings 210 and 212 define the position of the paper on roller 184.Sixth, the paper is threaded under light shield 196, across surface 198,under light shield 200, over take-up metering roller 188 and onto theempty paper core on take-up roller 190. The paper is wound onto roller190 with the emulsion side in.

The proper amount of paper advanced after each print exposure isdetermined by the number set by the PAPER FEED COUNT switches 82 on thecontrol panel 20 (see FIG. 4) if the PAPER AUTO/MAN switch 84 is on the"MAN" position. If switch 84 is in the "AUTO" position, the paper feedis determined by indicia on paper mask 50.

The amount by which the paper has advanced is sensed by means of a disk214 which is attached to supply metering roller 184. Disc 214 has aplurality of equally spaced rectangular apertures around its periphery.A light eitting diode (LED) and a photosensor (not shown) are positionedon opposite sides of disc 214. As supply metering roller 184 and,therefore, disc 214 turn, light from the LED reaches the photosensor andan electrical pulse is generated each time an aperture passes. Bycounting pulses, it is possible to determine how far the paper hasadvanced. When the paper has advanced by the amount determined by thenumber set by either the PAPER FEED COUNT switches (manual operation) orthe indicia on the paper mask (automatic operation), the drive to motor194 is removed and brake 192 is energized, thereby halting the paperfeed.

As mentioned above, indicia on the paper mask 50 determine the distancethe paper will travel when the PAPER AUTO/MAN switch is in the AUTOposition. FIG. 13 is a top view of a typical paper mask.

Paper mask 50, as shown in FIG. 13, has a mask opening 216 which definesthe paper to be exposed. The size of opening 216 varies from mask tomask. Typical sizes include 31/2 × 21/2, 31/2 × 5, 5×4, 5×7, 8×8, 8×10,and 9.4 × 11.8 inches.

Near the rear edge of mask 50 are three groups 218, 220 and 222 ofthreaded holes. Groups 218 and 220 each contain four threaded holes andgroup 222 contains three threaded holes. When paper mask 50 is installedon the paperdeck, the holes are positioned directly over Paper FeedMicroswitches. Screws may be inserted in the holes to depress selectedones of the Paper Feed Microswitches. In the preferred embodiment group218 represents "ones," group 220 represents "tens" and group 222represents "hundreds" in the desired feed count. The number is in binarycoded decimal (BCD) format.

The feed count on the mask may be factory set if desired. It isgenerally preferable, however, to allow the photofinisher to set thefeed count. This allows the photofinisher to "fine tune" the feed lengthfor each mask to achieve his standard border size. Variousphotofinishers prefer slightly different border sizes, and allowing thephotofinisher to set the screws in groups 218, 220 and 222 accommodatesthese variations. Once the feed count has been set (either at thefactory or by the photofinisher) it generally will not be changed.

Although the threaded hole-screw-microswitch arrangement is a preferredtechnique of automatically controlling feed length, other techniques maybe used. For example, other forms of indicia and indicia sensors may beused. In each case, the indicia is associated with the paper mask andprovides the desired feed count for that particular mask size.

An alternative to individual masks is a "universal" paper mask which isadjustable for various print sizes. FIGS. 14 a and 14b show top and sideviews of a universal paper mask for use with the printer of the presentinvention.

The universal mask includes base members 224 and 226, which are held bylocating bar 228 and rear stiffening bar 230. Left and right lightshields 232 and 234 are slidable to define the sizes of opening 236.Attached to the edges of light shields 232 and 234 are light sealbrackets 238 and 240, respectively. The positions of light shields 232and 234 are determined by locator pins 242 and 244, respectively, whichare inserted into the desired holes in locator bar 228.

When the universal mask of FIGS. 14a and 14b is used, the MAN ratherthan the AUTO paper feed is used. In other words, the paper feed lengthis determined by the paper feed count switches 82 on the control panel20 (FIG. 4) rather than indicia associated with paper mask.

Electrical System

FIGS. 15-21 are schematic diagrams for the major electrical subsystemsof the printer. Each Figure preferably represents an individual circuitboard.

(1) Control Panel

FIG. 15 is a schematic diagram of the control panel. The physicalappearance of the control panel is shown in FIG. 3.

POWER switch 52, when in the power on position, energizes the power onrelay, which turns on the printer power supply and lamphouse fan.Indicator lamp 246 is energized when power switch 52 is in the power onposition.

EXPOSURE switch 54 is a momentary switch which provides the EXP SWsignal to the cycle control circuit when depressed. The EXP SW signalinitiates one or more print cycles, provided that the negative mask isin place.

CLEAR switch 56 is a momentary switch which provides the CLEAR SW signalto the cycle control circuit. This signal clears the electronic logicwhen an exposure or paper feed cycle is begun but not completed.

PAPER switch 58 is a momentary switch which provides the PAP FD SWsignal to the paper feed control circuit. The PAP FD SW signal initiatesa paper feed cycle.

When PRINT/FOCUS switch 60 is in the PRINT position, normal operation ofthe printer is permitted. The FOCUS position, which is used only whilefocusing the printer, causes indicator lamp to be energized.

COLOR-B/W switch 62 selects a color or black and white printing modefrom the printer. K COLOR SW signal is provided by COLOR-B/W switch 62to the cycle control circuit.

RUN/TEST switch 64 provides the RUN SW signal to the blue, green and redexposure control circuits, the cycle control circuit, and the paper feedcontrol circuit. This signal enables or disables the automatic paperfeed and the shutter paddle.

Preview lamp control 66 is a variable resistor. Clockwise movement ofthe control knob moves the wiper arm to reduce the resistance andthereby increase the intensity of the preview lamp.

Color controls 68a, 68b and 68c are variable resistor circuits whichprovide the TIMB (R), TIMB (G) and TIMB (B) signals to the red, greenand blue exposure control circuits, respectively. These signals regulatethe exposure time for the red, green and blue emulsion layers of thephotographic print paper. A clockwise turn of a color control increasesthe value of the corresponding TIMB signal, which results in an increasein color density.

Coarse density control 70 is a multiple position switch. Depending onthe position selected, one of the coarse density signals CDEN1-CDEN8, isa "1. " Signals CDEN1-CDEN8 are provided to the red, green and blueexposure control circuits. Each position of control 70 yields anexposure time twice as long and a density increase of 0.7 points fromthe position immediately below it.

Fine density control 72 is a multiple position switch having threeseparate sections for red, green and blue. The FDEN (B), (G) and (R)signals are provided to the blue, green and red exposure controlcircuits, respectively. Each position of the switch connects a differentvalue of capacitance. The value of the capacitance increases with eachposition. Exposure time is increased by about 5 percent and densityabout 0.04 points with each increment.

Indicator lamps 78a, 78b and 78c are light emitting diodes (LEDs) whichshow the duration of the exposure in the red, green and blue colorchannels, respectively. They are energized by the EXPLED (R), (G) and(B) signals from the red, green and blue exposure control circuits. Whenthe exposure begins, all three are lit; each goes out as the exposure inits color channel is completed.

(2) Sensor Ring and Exposure Control Circuits

FIG. 16 is a schematic diagram of the photocell sensor ring. The "RSENSOR" and "G SENSOR" signals are produced by three CdS photocellseach. Four CdS photocells produce the "B SENSOR" signal.

FIG. 17 shows the blue exposure control circuit. The red and greenexposure control circuits are identical to the blue exposure controlcircuit. The following discussion, therefore, will apply to all threecircuits although specifically discussing the blue exposure controlcircuit.

The blue exposure control circuit receives signals from the controlpanel, the cycle control circuit (discussed later) and from thephotocell sensor. The signals received from the control panel includethe RUN SW, TIMB (B), FDEN (B), and coarse density signals CDEN1-CDEN8.From the cycle control circuit the exposure control circuit receives theEXP COMP, 8K CLOCK, CLEAR and STA EXP (GREEN RED) signals. The SSIsignal is received from the photocells.

The output signals from the exposure control circuit are the FILTER SOL(B) signal (which energizes the blue filter solenoid), the EXP (BLUE)signal (which is used by the cycle control circuit), and the EXPLED (B)signal (which lights indicator lamp 78c on the control panel).

In many of the prior art printer systems, the exposure time iscontrolled automatically by the photocell signal by means of an analogintegration of the photosignal. The integrated signal level required toterminate exposure is determined by density and color controls.

This technique, however, has certain drawbacks. In particular, in mostphotographic systems changes in density and color are on a logarithmicrather than a linear scale. Since the analog integration technique isnot logarithmic, additional circuit complexity is required to convertthe settings at the density and color controls, which readlogarithmically, to the appropriate analog integration signal level.

The exposure control circuit of FIG. 17 overcomes these problems bymeans of an oscillator-counter system. Exposure oscillator 250 producesoutput pulses at a rate which is determined by the SSI, TIMB (B) andFDEN (B) inputs.

Inputs to exposure oscillator 250 receive SSI (B), TIMB (B) and FDEN(B). Resistor R1 is connected between the SSI (B) and FDEN (B) inputs,capacitor C1 is connected between FDEN (B) and ground, and capacitor C2is connected between TIMB (B) and ground. The FDEN (B) input connectsadditional capacitance in parallel with C1. The setting of the finedensity control 72 on the control panel determines the amount of thatcapacitance.

The output pulses from exposure oscillator 250 are received by binarycounter 252. The Q6-Q13 outputs of counter 252 are NANDed with thecoarse density signals CDEN1-CDEN8 by NAND gates 254-261. Depending uponthe position of the coarse density switch, only one of the CDEN inputswill have a +12 volt level. This level is applied through one of theinput resistors R2-R9 to an input of one of NAND gates 254-261. Theoutputs of NAND gates 254-261 are NORed by NOR gates 262, 264 and 266 sothat the output of NOR gate 266 goes to "0" when a "1" at an output ofcounter 252 coincides with the "1" on one of the CDEN inputs.

The effect of the oscillator-counter arrangement shown in FIG. 17 isthat each step of the coarse density switch increases the count requiredby a factor of 2. A logarithmic type of exposure time control isachieved.

When the output of NOR gate 266 goes to "0," it causes exposure andpulse generator 268 formed by flip-flops 270 and 272 and NAND gate 274to produce a positive pulse of about 1.2 ms duration. Exposure and pulsegenerator 268 receives the 8K CLOCK input, which is a 8KHz clock signalgenerated in the cycle control circuit, and which is inverted byinverter 275.

The pulse from the exposure end pulse generator 268 is applied to NORgate 276. The other two inputs to NOR gate 276 are the CLEAR and theRSTP EXP inputs. Under normal operation, both of the inputs remain "0"throughout the cycle, and the output of exposure end pulse generator 268determines the output of NOR gate 276. The RSTP EXP input is an optionalremote stop exposure signal which allows control of exposure time by anexternal control.

The output of NOR gate 276 is applied to the Reset input of exposureflip-flop 278. The Set input receives the output of NOR gate 280, whichNORs the STA EXP (GREEN RED) and RSTA EXP signals. The STA EXP (GREENRED) which is received from the cycle control circuit, normally startsthe exposure cycle. The RSTA EXP is an optional remote start exposuresignal to permit external control.

The commencement of exposure, designated by either the STA EXP of RSTAEXP signal going to "1" and the output of NOR gate 280 going to "0" setsexposure flip-flop 278. The Q output goes to "1" and the Q output goesto "0" .

When the Reset pulse is received from NOR gate 276, exposure flip-flopis reset. This causes Q output to go to "0," which indicates that theblue exposure is complete and should be terminated. The EXP(BLUE)output, which is sent to the cycle control, is derived from the Q outputof exposure flip-flop 278. The Q output is connected to the reset inputof counter 252, thereby halting further operation of counter 252.

When exposure flip-flop 278 is reset, a set signal is generated byfilter energize pulse generator 282 and is applied to the Set input offilter paddle flip-flop 290.

The Q output of exposure flip-flop 278 is also connected to filterenergize pulse generator 282, which is formed by flip-flops 284 and 286and NAND gate 288. Filter paddle flip-flop 290 is reset by the EXP COMPsignal is inverted by inverter 292 and applied to one input of NOR gate294. The CLEAR signal is applied to the other input. The output of NORgate 294 is applied to the Reset input of filter paddle flip-flop 290.

The output of filter paddle flip-flop 290 is NANDed by NAND gate 296with the RUN SW signal, which is inverted by inverter 298. When the RUNswitch is in the RUN position and filter paddle flip-flop 290 is set,the output of NAND gate 296 goes to "0," which causes the blue filtersolenoid to be energized. The FILTER SOL (B) signal is derived from theoutput of NAND gate 296 by inverter 300 and resistor R17.

The exposure control circuit includes three indicator lamp circuits andthe drive circuit which produces the EXPLED (B) signal which drivesindicator 78c on the control panel. The first of the three indicatorcircuits includes inverter 302, resistor R18, and light emitting diodeDS1. DS1 indicates the duration of the exposure in the blue colorchannel. When exposure flip-flop 278 is set, DS1 is lit, and it remainslit until exposure flip-flop 278 is reset.

DS1 is lit concurrently with indicator 78c on the control panel. Thedrive circuit which produces the EXPLED (B) signal includes inverter304, resistors R19, R20 and R21 and transistor Q1.

The second indicator circuit in the exposure control circuit is theexposure oscillator indicator circuit, which includes DS2, inverter 306and resistor R22. DS2 is a LED which flashes when DS1 is lit and counter252 is counting. DS2 indicates the cyclic electric pulse which times theexposure. Some exposure times are too fast for the flashing to bevisible.

The third indicator circuit includes light emitting diode DS3, resistorR23, and inverter 308. DS3 lights when the blue channel has completedits exposure and another channel is still active (i.e. filter paddleflip-flop 290 is set). DS3 goes out when all channels have completedtheir exposure cycle (i.e. filter paddle flip-flop is reset).

The three exposure control circuits, together with the cycle controlcircuit discussed later, provide accurate and effective exposure timecontrol for the three color channels. One advantageous feature notpresent in previous printers is that only the first two color channelsto complete their exposure time cause their respective filter solenoidsto drive their filter paddles into the light path. Rather than activatethe filter solenoid, the last channel causes the shutter paddle to bedriven into the light path. This terminates the exposure without theredundancy of driving the last of the three filter paddles into thelight path.

This feature is accomplished by the use of filter energize pulsegenerator 282 and filter paddle flip-flop 290. The FILTER SOL signal isderived from filter paddle flip-flop 290 rather than directly fromexposure flip-flop 278.

The delay between the reset of exposure flip-flop 278 and the productionof a set pulse by filter energize pulse generator 282 to filter paddleflip-flop 290 is very short, but it is long enough to allow the cyclecontrol circuit to receive the EXP signal and to produce the EXP COMPsignal if the other two channels have already completed their exposure.If the EXP COMP signal is generated, the filter paddle flip-flop 290 isreset and the shutter paddle solenoid rather than the filter paddlesolenoid is actuated.

(3) Solenoid Driver

FIG. 18 shows a schematic diagram of a typical solenoid driver used inthe printer. This solenoid driver is used to drive the filter paddle,shutter paddle and paper feed solenoids. The solenoid driver of FIG. 18includes transistor Q2, diodes CR1 and CR2, zener diode CR3, resistorR24 and light emitting diode DS4.

(4) Aperture Pulse and Paper Feed Circuits

FIG. 19 shows the aperture pulse circuit which produces pulses as theapertured disk 214 (of FIGS. 11a-11c) attached to supply metering roller184 turns. By counting the pulses generated, it is possible to determinehow far the print paper has been advanced.

The aperture pulse circuit of FIG. 19 includes a LED-photoDarlingtonpair PS1 which, together with resistor R25, produces a pulsingphotosignal as the apertured disk 214 turns. The LED of PSI is mountedon one side of the disk and the photoDarlington is mounted on the otherside, so that light from the LED reaches the photoDarlington each timean aperture in the disk passes.

The output of PS1 is processed by an amplifier circuit formed by R26,R27 and R28 and Al, and a comparator circuit formed by R29-R34, C3 andA2.

The output of the comparator circuit controls a differential line driverformed by resistors R35 and R36 and transistor Q3. The PAP ENC + and PAPENC - output lines which are supplied to the paper feed are derived fromthe emitter and collector, respectively, of Q3. When Q3 is turned on,the voltage between the two lines is approximatey OV; when Q3 is turnedoff, the voltage is approximately 5V.

An indicator circuit formed by light emitting diode DS5 and resistor R37is connected between the PAP ENC + and PAP ENC - lines. DS1 flashes onand off as the paper supply metering roller and the apertured disk move.DS1 indicates that paper travel information (i.e. pulses) is beingtransmitted to the paper feed control circuit.

FIGS. 20a and 20b are schematic diagrams of the paper feed circuitry.This circuitry controls the operation of the paper feed mechanism inboth the automatic and manual paper feed modes of operation.

The paper feed circuitry of FIG. 20a receives the desired feed length inbinary coded decimal form from both the paper mask Microswitches, whichsense the feed length encoded on the paper mask and the paper feed countswitches 82 (shown in FIG. ). The "1's," "10's" and "100's" inputs areapplied to quad AND-OR select circuits 310, 312 and 314 respectively.The inputs from the paper feed count switches are applied to the "A"inputs and the inputs from the paper mask Microswitches are applied tothe "B" inputs.

The outputs of the quad AND-OR selectcircuits 310, 312 and 314 are equalto either their "A" or their "B" inputs, depending on the state of theMAN PFL signal. This signal is produced by the PAPER AUTO/MAN switch 84on the control panel (FIG. 4). When the PAPER AUTO/MAN switch is in theMAN position, the MAN PFL signal, which is applied to the K_(A) andK_(B) inputs of select circuits 310, 312 and 314 by means of resistorR38 and inverter 316, causes the "A" inputs to be outputted. Conversely,when the PAPER AUTO/MAN switch is in the AUTO position, the MAN PFLsignal causes the "B" inputs to be outputted by select circuits 310, 312and 314.

The outputs of select circuits 310, 312 and 314 are applied to theinputs of "1's," "10's" and "100's" counters 318, 320 and 322,respectively. Counters 318, 320 and 322 are countdown counters, whichcount down to zero from the number applied to their inputs.

The load signal which causes the inputs from select circuits 310, 312and 314 to be loaded into counters 318, 320 and 322 is derived from NORgate 324. The inputs of NOR gate 324 cause a load signal to be producedby NOR gate 324 whenever an exposure is completed or the CLEAR switchhas been energized.

The counting of counters 310, 312 and 314 is controlled by the PAP ENC +and PAP ENC - signals from the aperture sensing circuit. Each pulse onthese two inputs indicates that the paper supply metering roller hasadvanced by a predetermined increment. This pulse is received by theinterface circuitry including resistor R39, capacitor C4, zener diodeCR4, optoisolator 326 and inverter 328 and is applied to the count-downinput of "1's" counter 318.

With each pulse produced by the aperture sensing circuit, the countstored in counters 318, 320 and 322 is decremented by one. The outputsof counters 318, 320 and 322 are NANDed by NAND gates 330, 332 and 334.The outputs of gates 330, 332 and 334 are NANDed by NAND gate 336. Whenthe outputs of counters 318, 320 and 322 all reach zero, therefore, theoutput of NAND gate 336 goes to "O." This indicates that the desiredpaper feed length has been attained and paper feed should be halted.

Both the uninverted and the inverted outputs of NAND gate 336 are usedby the remainder of the paper feed circuitry. The inverted output isproduced by inverter 338.

The paper feed circuitry includes an indicator circuit formed byinverter 340, resistors R40 and R41 and light emitting dioe DS6. As thepaper supply metering roller moves, DS6 flashes on and off. When theroller stops, this light may remain on or go out, depending on theposition of the paper supply metering roller. When DS6 is flashing, itindicates that information is being supplied to the paper feed circuitryfrom the aperture sensing circuitry to determine the length of paperfeed.

Indicator DS6 works in conjunction with indicator DS5 in the aperturesensing circuit. When DS6 is on, DS5 is off, and when DS5 is on, DS6 isoff.

FIG. 20b shows the remainder of the paper feed circuitry. The paper feedoperation is generally controlled by paper feed flip-flop 342. Whenpaper feed flip-flop 342 is "set," paper is fed; when it is reset, paperfeed is halted.

Paper feed flop-flop 342 may be set either manually or automatically.The manual commencement of paper feed is achieved by depressing PAPERswitch 58 on the operator panel. This generates the PAP FD SW signalwhich, along the the MEXP and 8MSCL signals from the cycle controlcircuit, cause a set signal to be aplied to paper feed flip-flop 342.

The PAP FD SW and 8MSCL (clock) signals are applied to paper feed filter344, which is both a time delay filter and a pulse generator. Contactbounce and other noice on the PAP FD SW line is filtered and a pulse isproduced by paper feed filter 344, which includes resistors R42-R44 andflip-flops 346, 348 and 350.

The two outputs of paper feed filter 344 are NANDed with the MEXP signalby NAND gate 352 and applied to the set input of paper feed flip-flop342 through NOR gate 354. The MEXP signal prevents a manual paper feedfrom beginning as a result of the PAPER switch 58 being depressed if anexposure is still taking place. This is an important inhibit feature,since the commencement of paper feed during exposure would ruin theprint.

The automatic commencement of paper feed is achieved by the RUN SW andEXP COMP signals, NAND gate 356 and NOR gate 354. When the RUN/TESTswitch 64 is in the RUN position and the cycle control circuit generatesthe EXP COMP signal, which indicates that the exposure is complete, NANDgate 356 and NOR gate 354 provide a set signal to paper feed flip-flop342, thereby automatically commencing the paper feed.

The set input to paper feed flip-flop 342 is also supplied, throughinverter 358, to NOR gate 324 shown in FIG. 20a. When paper feedflip-flop 342 is set, a load signal is also provided by NOR gate 324 tocounters 318, 320 and 322. This load signal causes the desired paperfeed count to be loaded into counters 318, 320 and 322 at thecommencement of paper feed.

Paper feed is halted by a Reset signal from NOR gate 360 to the Resetinput of paper feed flip-flop 342. NOR gate 360 has three inputs,thereby providing three different means of halting paper feed.

The first input to NOR gate 360 is the CLEAR signal. As previouslydiscussed, the CLEAR signal halts all operations and clears all of thecircuits so that a new print cycle can be commenced from the beginning.

The second input is the output of NAND gate 336 of FIG. 20a, which isinverted by inverter 362. When the desired paper feed count has beenattained the output of NAND gate 336 goes to "0" and and the secondinput to NOR gate 360 goes to "1," thereby resetting paper feedflip-flop 342. Under normal operation, it is the second input whichcauses paper feed flip-flop 342.

The third input resets paper feed flip-flop 342 and thereby terminatesthe paper feed after a predetermined time period. This is a safetyfeature which prevents the entire paper roll from being fed in the eventthat the signal to the second input of NOR gate 360 is not producedduring the predetermined time period. The failure to produce the signalto the second input can be caused by a variety of possible mechanicaland electrical failures or malfunctions. The third input to NOR gate 360prevents such a falure or malfunction from causing excessive paper feed.

The third input is produced by paper feed time out counter 364, which isformed by resistors R45, R46 and R47, binary counter 366, flip-flops 368and 370 and NAND gate 370. In one preferred embodiment about 7 secondsis the time peeriod before paper feed time out counter 364 generates thethird input signal which resets paper feed flip-flop 342. When paperfeed flip-flop 342 is set, counter 366 is reset and counter 366 beginsto count up at a rate determined by the 512 MSCL clock signal. Whencounter 366 reaches a predetermined count, it produces an output to thepulse generator formed by flip-flops 368 and 370 and NAND gate 372. Theoutput of the pulse generator is applied to the third input of NOR gate360, and is also provided to the cycle control circuit at the PFT OUTsignal.

The output of paper feed flip-flop 342 is inverted by inverter 374 toproduce the PAP FD signal to the cycle control circuit. The output ofinverter 374 is inverted by inverter 376 to produce the PAPER FEED RELAYsignal, which controls operation of the paper feed motor.

The feed control circuit also produces a BRAKE signal which controlsoperation of the paper brake. The BRAKE signal is generated by NOR gate378, inverter 380, and resistor R48. One input to NOR gate 378 isderived from the output of inverter 374 and the other input is the PBDISsignal which is inverted by inverter 382.

The brake is released by the BRAKE signal when paper feed flip-flop 342is set. It is also released in response to the PBDIS signal, which isproduced by the supply roller disengage switch. The PBDIS signal isgenerated only during initial threading of the print paper, and causesthe brake, but not the paper drive motor, to be released to facilitatepaper threading.

Another signal provided to the cycle control circuit by the feed controlcircuit is the PFSTR signal. Inverter 384 inverts the output of NANDgate 356 to produce the PFSTR signal.

An indicator circuit formed by inverter 386, resistor R49 and lightemitting dioe DS7 is driven by the inverted output of paper feedflip-flop 342. DS7 is lit when power is being applied to the paper feedmechanism to cause a paper feed.

The paper feed indicator 74 on the control panel is also lit during apaper feed. An indicator drive circuit formed by inverter 388, resistorsR50 and R51, and transistor Q1 produces the PAP FD LED signal whichdrives paper feed indicator 74.

FIG. 20b also shows optional film feed and paper punch control circuits.The film feed circuit automatically advances the negative film from onenegative to the next. The paper punch circuit drives a paper punch whichprovides indexing punched indicia on the print paper to allow subsequentautomatic cutting of the print paper into individual prints.

The film feed control circuit includes resistors R52-R57, NAND gate 390,inverters 392, 394 and 396, NOR gates 398 and 400, and film feedflip-flop 402. The film feed control circuit receives the FILM FEED ON,STA FLFD, STP FLFD, and EXP COMP signals and produces the FILFD and FILMFEED DR signals.

The FILFD and FILM FEED DR signals are derived from the outputs of filmfeed flip-flop 402. When the automatic film feed is in operation, asindicated by the FILM FEED ON signal being "0," and the EXP COMP is "0"(indicating the exposure is complete), film feed flip-flop 402 is set bymeans of NAND gate 390 and NOR gate 398.

Film feed flip-flop 402 may also be set by the STAFLFD signal, whichapplies a set signal by means of inverter 392 and NOR gate 398. TheSTAFLFD signal is produced manually by means of a film feed start switch(not shown).

Film feed flip-flop 402 is reset, thereby halting film feed, by a resetsignal from NOR gate 400. The inputs to NOR gate 400 which may producethe reset signal are the STPFLFD and the CLEAR signals.

The FILFD signal is directed to the cycle control circuit whichcoordinates the operation of the automatic film feed with the remainderof the printer system. The FILM FEED DR signal controls the operation ofthe film feed drive mechanism.

The indicator circuit formed by inverter 394, resistor R56 and lightemitting diode DS8 is driven by an output of film feed flip-flop 402.DW8 is lit when the negative film is being fed.

The optional punch drive circuit produces CUT MARK END OR MARK and PUNCHsignals. The CUT MARK signal is applied to a solenoid drive which causesa "cut" punch mark indicating the position of each print. The END ORMARK is applied to a solenoid which causes an "end of order" mark to bemade on the print paper to indicate the end of an order. The "cut" and"end of ordeer" marks are used if the print paper is to be cut by anautomatic print cutter.

The PUNCH signal is provided to the cycle control circuit, which delaysthe commencement of a new exposure until the punch operation iscompleted. If this delay were not provided, an exposure might beginwhile the punch is operating. Since the punch causes some vibration ofthe paper deck, commencement of exposure during punching could haveadverse effects upon the quality of prints.

The punch control circuit includes punch duration flip-flop 404, end oforder flip-flop 406, punch duration counter 408, resistors R58-R65,flip-flops 410 and 412, NAND gates 414-416 and 418, NOR gates 420, 422,and 424, inverters 426, 428 and 430, and light emitting diode DS9.

The PUNCH and CUT MARK signals are derived from the output of punchduration flip-flop 404. The solenoid drive for the paper punch isenergized when punch duration flip-flop 404 is set.

Punch duration flip-flop 404 is set by an "0" at the output of NOR gate420. One input of NOR gate 420 is derived from the output of NAND gate416, which NANDs the PRT LAMP signal with the output of inverter 338 ofFIG. 20a. The other input to NOR gate 420 is produced by the pulsegenerator formed by flip-flops 410 and 412 and NAND gate 414.

Punch duration flip-flop 404 is reset by the CLEAR signal or by theoutput of punch duration counter 408. These two signals are NORed by NORgate 422 and applied to the Reset input of punch duration flip-flop 404.

Under normal operation, the signal from punch duration counter 408resets punch duration flip-flop 404. Counter 408 is reset when punchduration flip-flop 404 is set, and begins to count up at a ratedetermined by the 16 MSCL clock signal. When counter 408 reaches apredetermined count, it generates a signal which causes punch durationflip-flop 404 to be reset.

End of order flip-flop 406 is set by the END OF ORDER signal. It isreset by the output of NOR gate 424, which has as its inputs the CLEARsignal and the EXP COMP signal which is inverted by inverter 426.

NAND gate 418 NANDs outputs from punch duration flip-flop 404 and end oforder flip-flop 406. The END OR MRK signal is produced when punchduration flip-flop 404 is reset and end of order flip-flop 406 is set.

An indicator circuit formed by inverter 428, resistor R64 and lightemitting diode DS9 is driven by the output of end of order flip-flop406. DS9 lights when the end of an order occurs.

(5) Cycle Control

FIGS. 21a and 21b are schematic diagrams of the cycle control circuit.The cycle control coordinates the operation of the various circuitswhich have been discussed previously. It contains, therefore, severaldifferent circuits which provide signals to the other circuits, such asthe exposure control and paper feed circuits.

One of the circuits of the cycle control is the clock oscillator circuit432 formed by resistors R66, R67 and R68, capacitors C5 and C6, 8kHzoscillator 434 and clock divider counter 436. The clock oscillatorcircuit 432 produces the 8K CLOCK, 4MSCL, 8 MSCL, 16 MSCL and 512 MSCLclock signals.

A second circuit in the cycle control is the clear circuit, whichreceives the CLEAR SW signal from the operator panel and generates theCLEAR signal which clears the logic of the various control circuits andallows a new cycle to be commenced. The clear circuit includes resistorR69, a clear switch input filter formed by flip-flops 438 and 440, apower-on clear circuit formed by R70, C7 and inverters 442 and 444 andNOR gate 446.

The CLEAR SW signal is filtered by flip-flops 438 and 440 to preventcontact bounce and other noise which may produce erroneous signals. Theoutput of flip-flop 440 is applied to one of the inputs of NOR gate 446,whose output is the CLEAR signal. When the clear switch is depressed onthe operator panel, the output of flip-flop 440 goes to "0" and theCLEAR signal is generated.

The CLEAR signal is also automatically produced when power is turned on.This ensures that all of the control circuits are ready when a cycle iscommenced. The power-on clear circuit formed by R70, C7 and inverters442 and 444 provides the second input to NOR gate 446,. When power isturned on, this second input goes to "0," and a clear signal isproduced.

A third circuit in the cycle control is the print-counter drive circuit.This circuit receives the RUN-SW signal from the operator panel, thePFSTR signal from the paper feed control, and the COUNTER SW signal fromthe control panel and provides the COUNTER COIL signal to the controlpanel. The COUNTER COIL signal decrements the multiple print counter onthe control panel.

The RUN SW signal is received by R71 and applied to input of NAND gate448. The other input to NAND gate 448 is the COUNTER SW signal, whichhas been filtered by a filter formed by R72, inverter 450 and flip-flops452 and 454.

The output of NAND gate 448 is NANDed by NAND gate 456 with the CLEARsignal, which has been inverted by inverter 458. The inverted CLEARsignal is normally "1" and, therefore, the states of the RUN SW andCOUNTER SW signals normally control the output of NAND gate 456. In theabsence of a CLEAR, the output of NAND gate 456 is "0" when RUN SW is"0" (indicating that the RUN switch is in the RUN position) and COUNTERSW is "0" (indicating that a non-zero number of prints are indicated onthe multiple print counter).

The output of NAND gate 456 is NANDed with the PFSTR signal by NAND gate459. The PFSTR Signal levels are determined by input resistor R73, whichis tied to a +12 v supply.

When the output of NAND gates 459 is "1," it sets counter coil timerflip-flop 460. This causes the counter coil driver formed by inverter463, resistors R74 and R75, zener diode CR4, diode CR5 and transistor Q5to produce a "0" COUNTER COIL signal. This signal causes the multipleprint counter to be decremented.

Counter coil timer flip-flop 460 is reset and decrementing of themultiple print counter is halted by either the CLEAR signal or theoutput signal from counter coil timer 462. These two signals are appliedto the reset input counter coil timer flip-flop 460 by means of NOR gate464 and inverter 466.

The normal reset of counter coil timer flip-flop 460 is by counter coiltimer 462, which is a binary counter 462. When counter coil timerflip-flop 460 is set, counter coil timer 462 is reset to zero. The 8MSCLclock signal drives counter coil timer 462 and when counter coil timerhas counted up to a predetermined number, an output "1" is producedwhich causes counter coil timer flip-flop 460 to be reset. By thisarrangement, the multiple print counter decremented by only one digitfor each print cycle.

A fourth circuit in the cycle control is the exposure delay circuitformed by flip-flops 468 and 470, NAND gate 472, NOR gate 474, inverters476 and 478, exposure delay flip-flop 480, and exposure delay timer 482.The exposure delay circuit provides an approximately 178 second delaybefore exposure is commenced so that the entire printer system hasstabilized when exposure begins.

A fifth circuit receives the EXP (RED), EXP (GREEN) and EXP (BLUE)signals from the respective exposure control circuits and the COLOR SWsignal from the operator panel. This circuit, which includes resistorsR76-R82, inverters 484, 486, 488, 490, 492, 494 and 496, NAND gates 498,500 and 502, NOR gates 504 and 506 produces RED CLOCK, RED CLOCK DR,GREEN CLOCK, GREEN CLOCK DR, BLUE CLOCK and BLUE CLOCK DR signals. Thesesignals control an optional timing clock which displays the time elapsedfor each of the three color channels. When the COLOR-B/W switch or theoperator panel is in the COLOR position, the displays for the threechannels are allowed to display different exposure times. On the otherhand, when the COLOR-B/W is in the B/W position, only the blue channelis being used and all three displays are caused by the logic to displaythe exposure time of the blue channel. This prevents any confusion whichmight otherwise occur when black and white prints are being made.

A sixth circuit receives the EXP (RED), EXP (GREEN), EXP (BLUE), FOCUSSW and RUN SW signals and produces the SHUTTER SOL and EXP COMP signals.As discussed previously in the description of the exposure controlcircuits, when the printer is in the COLOR mode, the first two colorchannels to complete their exposures cause filter paddles to be driveninto the light path. The last color channel to complete its exposurecauses the shutter paddle rather than the third filter paddle to bedriven into the light path.

When the EXP COMP signal is "0," it indicates that all three colorchannels have completed their exposures. The EXP COMP signal is providedto the exposure control circuits to cause the shutter paddle rather thanthe last filter paddle to be driven into the light path. The EXP COMPsignal is also provided to the paper feed control to inhibit paper feeduntil exposure is complete.

To produce the EXP COMP signal, the EXP (RED), EXP (GREEN) and EXP(BLUE) signals are NANDed by NAND gate 508. The output of NAND gate 508is applied to an exposure complete delay circuit formed by flip-flops510, 512, 514 and 156 and NAND gate 518. The EXP COMP signal is derivedfrom the output of NAND gate 518.

The SHUTTER SOL signal controls the solenoid which moves the shutterpaddle. To produce the SHUTTER SOL signal the Q output of flip-flop 510is NANDed by NAND gate 520 with the RUN SW signal which has beeninverted by inverter 522. The output of NAND gate 520 is applied to aninput of NOR gate 524. The second input to NOR gate 524 is the FOCUS SWsignal. Inverters 526 and 528 and resistor R84 produce the SHUTTER SOLsignal from the output of NOR gate 524.

The output of inverter 526 is also used to driven an indicator circuitincluding inverter 530, resistor R85 and shutter indicator DS10. Whenthe shutter solenoid is energized, indicator DS10 is lit. A malfunctionin the shutter can be traced quickly by viewing DS10 and a similarindicator on the shutter solenoid driver printed circuit board. Bothindicators should light when the shutter solenoid is energized.

The remaining circuitry of the cycle control produces the signalsrequired to start a print cycle. These signals include the STA EXP(BLUE), STA EXP (GREEN/RED), MEXP, PRT LMP RELAY and PRT LAMP signal.

These are three ways that a print cycle may commence: (1)AUTO--automatically when the neghold switch is depressed by an insertednegative mask; (2) MAN--manually when the EXPOSE switch on the operatorpanel is pressed; and (3) MULTIPLE PRINT--automatically after the firstprint cycle until the desired number of prints have been made.

In the AUTO mode, the NEG EXP SW signal from the neghold switch isreceived by resistor R86 and a NEG EXP SW filter and pulse generatorformed by flip-flops 532, 534 and 536 and NAND gate 538. The inputs toNAND gate 538 include the Q output of flip-flop 534, the Q output offlip-flop 536, the FOCUS SW signal from R83 and the AUTO SW signal fromthe control panel. When all inputs are "1," NAND gate 538 sets NEG EXPSTART flip-flop 540. The AUTO SW signal, therefore, inhibits the negholdswitch from setting the NEGEXP START flip-flop 540 when the EXPOSUREAUTO/MAN switch 86 on the control panel (SEE FIG. 4) is in the MANposition.

NEG EXP START flip-flop 540 is reset by an "0" output from NOR gate 542.The inputs to NOR gate 542 are the CLEAR and the STA EXP (BLUE) signals.NOR gate 542 also supplies its output to inverter 476 of the exposuredelay timer circuit discussed previously.

The output of NEG EXP START flip-flop 40 is supplied to one input eachof NAND gate 544 and NOR gate 546. The output of NAND gate 544 is usedin the production of the STA EXP (BLUE) and STA EXP (GREEN/RED) signals,while the output of NOR gate 546 is used in the production of PRT LMPRELAY and PRT LMP signals.

The logic circuitry used in conjunction with the MAN mode is generallysimilar to that used in conjunction with the AUTO mode. The circuitryincludes resistor R88, a MAN EXP SW filter and pulse generator formed byflip-flops 548, 550 and 552 and NAND gate 554, MAN EXP START flip-flop556 and NAND gate 558.

When the EXP SW signal goes low, it indicates that the EXPOSE switch hasbeen depressed, a negative mask is in place and the EXPOSURE AUTO/MANswitch is in the MAN position. This causes the MAN EXP SW filter andpulse generator to produce a pulse which sets MAN EXP START flip-flop556. The output of MAN EXP START flip flop 556 is applied to one inputeach of NAND gate 558 and NOR gate 546. NAND gate 558 performs afunction similar to that of NAND gate 544.

Like NEG EXP START flip-flop 540, MAN EXP START flip-flop 556 is resetby a signal from NOR gate 542. In other words, MAN EXP START flip-flopis reset by either a CLEAR or a STA EXP (BLUE) signal.

The MULTIPLE PRINT Mode is controlled by multiple print latch 560 andNAND gate 562. The D input of multiple print latch 560 is derived fromNAND gate 442 and is "1" when the RUN switch is in the RUN position andthe MULTIPLE PRINT COUNTER had a non-zero value. The clock input oflatch 560 is the STA EXP (BLUE) signal, the reset input is derived fromthe output of NAND gate 456. The output of multiple print latch 560 issupplied to one input each of NAND gate 562 and NOR gate 546.

NAND gates 544, 558 and 562 have their outputs NORed by NOR gate 564.The output of NOR gate 564 is inverted by inverter 566 and supplied toan exposure start filter and delay circuit formed by flip-flops 568,570, 572 and 574 and NAND gate 576. The output of NAND gate 576 is theSTA EXP (BLUE) signal.

When color prints are being made, the STA EXP (GREEN/RED) signal is alsoproduced. The STA EXP (BLUE) signal is NANDed by NAND gate 578 with theinverted COLOR SW signal from inverter 490. The output of NAND gate 578is inverted by inverter 580 to produce the STA EXP (GREEN/RED) signal.

The output signals from NEG EXP START flip-flop 540, MAN EXP STARTflip-flop 556 and MULTIPLE PRINT latch 560 are also used to produce thePRT LMP RELAY and PRT LMP signals. The three output signals, togetherwith the MEXP signal from inverter 582, are NORed by NOR gate 546. TheMEXP signal is "1" when an exposure is in progress. By NORing the MEXPsignal with the other three signals, the output of NOR gate 546 isprevented from changing when an exposure is in progress, even thoughflip-flops 540 and 556 and latch 560 may be reset during the exposure.

The output of NOR gate 546 is NORed with the FOCUS SW signal by NOR gate584. In turn, the output of NOR gate 584 is applied to one input of NANDgate 586. The other input to NAND gate 586 is an inhibit signal which,under normal operating conditions, is "1." The output of NOR gate 584,therefore, normally determines the output of NAND gate 586.

The PRT LMP signal, which is supplied to the paper feed control, isderived from the output of NAND gate 588. Also connected to the outputof NAND gate 588 is a lamp driver circuit formed by inverter 590,resistors R89, R90 and R91, indicator DS11, diode CR6 and transistor Q6.The PRT LMP RELAY signal to the print lamps is derived from thecollector of Q6.

Indicator DS11 operates in conjunction with the print lamps. When theprint lamps are at high intensity, DS11 is also at high intensity. Whenthe print lamps go to low intensity, DS11 goes to low intensity.

The cycle control includes inhibit circuitry which inhibits theproduction of STA EXP (BLUE), STA EXP (GREEN/RED), PRT LMP RELAY, andPRT LMP signals unless and until certain conditions exist. The inhibitof the PRT LMP RELAY and PRT LMP signals is achieved by the second inputto NAND gate 586. Similarly, the inhibit of the STA EXP (BLUE) and (STAEXP (GREEN/RED) signals is achieved by the second inputs to NAND gates544, 558 and 562.

The first portion of the inhibit circuitry includes input resistorsR92-R95, NOR gate 592, ERROR flip-flop 594, inverter 596 and anindicator circuit including inverter 578, resistor R96 and indicatorDS12. The four inputs to NOR gate 592 are the PFT OUT, ERROR (R), ERROR(G) and ERROR (B) signals. PFT OUT signal is from the paper feed circuitand is "1" when the paper feed time out counter 364 has stopped paperfeed because paper feed has begun and is not completed in apredetermined period of time. The ERROR (R), ERROR (G) and ERROR (B)signals are optional signals which are "1" if some type of error modeexists in the red, green or blue channel.

If any of the inputs to NOR gate 592 are "1," ERROR flip-flop 594 isset. This causes the second input to NAND gate 586 to be "0," whichinhibits the production of the PRT LMP and PRT LMP RELAYS signals. Inaddition, DS12 is lit when ERROR flip-flop 594 is set, therebyindicating an error condition exists.

ERROR flip-flop 594 is reset by the CLEAR signal, which is inverted andapplied to the reset of ERROR flip-flop 594 by inverter 596. Once ERRORflip-flop 594 is set, the printer will not function until a CLEAR signalhas been produced.

The second portion of the inhibit circuitry includes input resistorsR97-R100, NAND gates 600 and 602, inverter 604, NAND gate 606 and delayswitch S1. In order to an exposure to be started, ERROR flip-flop 594must be reset, the PUNCH signal must be "1," and the outputs offlip-flops 516 and 536 must be "1." In that case, the output of NANDgate 600 is "0."

All four inputs of NAND gate 600 (i.e. PAPER FILFD, EXPINH and theoutput of NAND gate 600) must be "0." If any of the four inputs is "1,"the exposure cannot be started.

The inhibit to production of the STA EXP (BLUE) and STA EXP (GREEN/RED)signals is delayed in the AUTO mode, may or may not be delayed dependingon the position of delay switch S1 in the MAN mode, and is not delayedin the MULTIPLE PRINT mode. The delay is provided by inverter 604, whichinverts the output of NAND gate 602 and NAND gate 606, which NANDs theoutput of inverter 604 with the output of exposure delay flip-flop 480of the exposure delay timer. This delay is of approximately 1/2 secondduration, which allows the printer systems to stabilize before theexposure is begun.

The delayed inhibit is applied to the second input of NAND gate 544 andto the second input of NAND gate 558 when delay switch S1 is in thedelay position. The output of NAND gate 602, which is the undelayedinhibit, is applied to the second input of NAND gate 562 and to thesecond input NAND gate 558 when delay switch S1 is in the NO delayposition.

In conclusion, the cycle control produces signals which coordinate theoperations of other electrical subsystems, such as the paper feedcontrol and the exposure controls. In addition, the cycle controlproduces signals which start and stop exposure and control the printlamps. The operation of the cycle control, and hence the printerelectrical systems in general, is inhibited in the event any one ofseveral potential error conditions exist.

TYPICAL OPERATOR PROCEDURES

The following procedures are typical of the procedures used daily by anoperator in making photographic prints with the printer of the presentinvention:

1. The day's work is sorted according to

a. Color or black and white printing,

b. Film size, and

c. Enlargement size.

This sorting prevents unnecessary set-up and paper changes.

2. The POWER switch 52 and the LAMP switch on the lamphouse are turnedto the ON position. The printer is allowed 30 minutes warmup time withthe lamps on.

3. The LAMP switch is turned to the OFF position.

4. The operator determines which lens is required for thenegative-to-print size desired. The lens is set to the proper "f" stopand installed in the printer.

5. PRINT/FOCUS switch 60 is set to the PRINT position.

6. The print paper is loaded and the proper size paper mask isinstalled. This operation must be accomplished in total darkness.

7. The LAMP switch is turned to the ON position.

8. The lensdeck is set to the proper position for the particular filmand enlargement size.

9. The paper deck is set to the proper position.

10. The clock ON/OFF switch is turned on the ON position.

11. The COLOR-B/W switch 52 is set to the desired position.

12. For black and white printing the color controls are set to"1616-16." For color printing the proper settings are derived from aset-up chart used by the operator. The set-up chart lists the desiredsettings which have been derived by experience, for various types offilms, print papers and enlargement sizes.

13. The density controls 70 and 72 are set to settings shown on theset-up chart.

14. The dichroic filters are either set completely out of the light pathfor black and white printing,or are set to the setting shown on theset-up chart for color printing.

15. The SENSOR ON/OFF switch 88 is set to the desired position.

16. The EXPOSE AUTO/MAN switch 86 is set to the desired position.

17. The RUN/TEST switch 64 is set to the TEST position. A negative isinserted into the negative mask; then the negative mask is slid to theprinting position (fully to the rear of the neghold base). The printlampand proper color controls are checked to see if they are functioning.During this test, the RUN/TEST switch disables the shutter and paperfeed so that print paper is not wasted. After the test, the negativemask is removed from the printer.

18. The RUN/TEST switch 64 is set to the RUN position.

19. The PAPER AUTO/MAN switch 84 is set to the desired position. Whenset to MAN, the FEED COUNT switches 82 must be set.

20. The multiple print counter 80 is set to the desired quantity ifmultiple prints are required.

21. At this point, tests for daily color balancing adjustments are madeprior to printing any customer orders.

22. A customer negative is placed into the negative mask (emulsion sidedown).

23. The negative mask is slid into the printing position. When theEXPOSE AUTO/MAN switch 86 is in the AUTO position, the print cyclebegins automatically; when in the MAN position, the EXPOSE switch 54must be pressed to start the print cycle. After exposure is compete, thepaper advances and another print cycle may be commenced.

24. After the final exposure, the PAPER switch 58 is used to advance thepaper at least 20 in. (500mm) to clear the paper mask area.

25. The exposed paper is removed from the printer in the followingmanner:

a. The LAMP switch is turned to the OFF position.

b. The printing room is darkened.

c. The print paper is cut between the take-up metering roller 188 andthe take-up roller 190.

d. The exposed paper is removed from the printer and processed, whileensuring that the paper is not further exposed by room light.

e. The remaining paper is rethreaded onto the take-up roller 190.

CONCLUSION

The improved photographic printer light source of the present inventionachieves higher intensity than prior art light sources without acorresponding increase in input power consumption. The light source usesa plurality of print lamps rather than one lamp. Heat is dissipated by aheatsink positioned around the lamps. A diffuser, which preferablyincludes a white porcelain diffuse reflector, diffuses the light fromthe lamps to provide essentially uniform light distribution at thenegative.

The higher intensity light produced by the light source of the presentinvention allows shorter exposure times. This results in faster, moreefficient and more profitable operation of the photographic printer.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

What is claimed is:
 1. A light source for a photographic printercomprising:a plurality of print lamps for providing light; filter meansfor selectively modifying colors of the light from the plurality ofprint lamps; heatsink means positioned around the plurality of printlamps for dissipating heat generated by the plurality of print lamps,the heatsink means comprising a blackened, baffled assembly positionedto receive and absorb heat radiated from the plurality of print lamps;blower means for cooling the heat sink means and the plurality of printlamps; a lamphouse enclosure within which the plurality of print lamps,the filter means, the heatsink means, and the blower means are mounted,the lamphouse enclosure having a window through which light from theplurality of print lamps is directed; diffuser means for diffusing lightfrom the plurality of print lamps to provide an essentially uniformlight distribution, the diffuser means being positioned to receive thelight passing through the window and including white porcelain diffuserreflector for diffusing the light and changing the progation directionof the light received through the window from essentially horizontal toessentially vertical and downward.
 2. The light source of claim 1wherein the plurality of print lamps, the filter means, the heatsinkmeans, and the blower means are mounted within a lamphouse enclosure. 3.The light source of claim 2 wherein the lamphouse enclosure has a windowthrough which light from the plurality of print lamps is directed. 4.The light source of claim 3 wherein the diffuser means is positioned toreceive the light passing through the window.
 5. The light source ofclaim 4 wherein the diffuser means changes the progation direction ofthe light received through the window from essentially horizontal toessentially vertical and downward.
 6. The light source of claim 1wherein the lamphouse enclosure includes vent means.
 7. The light sourceof claim 6 wherein the blower means directs air past the heatsink meansto the vent means, thereby cooling the heatsink means.
 8. The inventionof claim 1 wherein the light diffuser means further includes atransmissive light diffuser for receiving light diffusely reflected bythe white porcelain diffuse reflector and further diffusing the light.9. A light source for a photographic printer comprising:a lamphouseenclosure having at one end a window through which light is directed andat an opposite end vent means for exhausting hot air from the lamphouseenclosure; a plurality of print lamps positioned in the lamphouseenclosure to provide light through the window; filter means positionedin the lamphouse enclosure between the print lamps and the window forselectively modifying colors of the light from the print lamps; ablackened, baffled heatsink assembly positioned around and behind theprint lamps in the lamphouse to receive and absorb heat radiated fromthe print lamps; blower means positioned in the lamphouse enclosurebetween the print lamps and the vent means for directing air past theheatsink assembly to the vent means where the air is exhausted from thelamphouse heatsink assembly; and diffuser means for receiving lightpassing through the window and diffusing the light to provide anessentially uniform light distribution.